The present invention relates to a method of manufacturing a single piece aluminum alloy wheel rim for vehicle tires. Vehicle wheels constructed of aluminum alloys are quite popular due to their aesthetic appearance and light weight. Because aluminum alloys are not readily susceptible to welding due to the deleterious effect of the welding process on the strength of the metal, it has been standard practice to manufacture separately the disc or wheel center and the inner and outer rims and subsequently to assemble the component parts by a suitable fastening means such as a plurality of threaded bolts. Such wheels are commonly referred to as three-piece wheels.
Three-piece wheels generally comprise superposed radial directed flanges extending from the inner and outer rims which are secured to a peripheral mounting on the wheel center by the fastening means. The problems inherent in such structures are inadequate strength and leakage. Inadequate strength, in addition to the obvious safety problems, has prevented such wheels from employing a desirable positive wheel offset which is highly advantageous, particularly for front wheel drive vehicles, to provide a greater area for larger breaking drums for improved breaking performance while complying with existing wheel placement regulations. In an effort to solve these problems, numerous different three-piece wheel configurations have been developed. For example, U.S. Pat. No. 4,466,670 teaches a configuration which provides improved strength characteristics over previously developed three-piece wheels and employs a silicon seal to prevent leakage. Applicant's co-pending application Ser. No. 721,172 employs a rim design which provides sufficient strength to maximize the positive wheel offset. Nevertheless, regardless of the design, the necessity to manufacture and subsequently secure together the inner and outer rims necessarily increases the cost of manufacture. It would therefore be highly desirable to develop a method of manufacturing a single piece aluminum alloy rim for use with conventional alloy wheel centers which would reduce assembly time and the cost of manufacture while maximizing strength. Because such a rim requires a radial flange or base for its securement to the wheel center and aluminum alloys cannot be readily welded without weakening the resultant rim, such wheels have not been heretofore available. The method of manufacture disclosed herein provides such a single piece flanged rim.